High Voltage Isolators

Would these be the ones making connections between the isolated high voltage conductors and electrical earth? If so, the answer is "for the safety of those working on those particular conductors".

_{Get it wrong with HV, and it's half a day out with the Undertaker, assuming there is enough left to bury or cremate...}

Cremation is automatic at 220 kV.

" This is not just a function of the higher transmission voltages - it is also often, if not done at lower voltages as well ".

Very true. Good answer.

A common example is the typical home circuit breaker panel, a single or multiple branch circuits can be placed in the open or off position, while the main is in the closed or on position.

A switch yard is just a larger circuit breaker panel.

You don't really think they are gonna shut the juice off at the power plant just because someone down stream wants to work on the wiring.

Visual break.

Ask someone who actually works in a switch yard if they would trust an indicator on a circuit breaker as their only means of isolation. Look into the appropriate codes and standards for switch yards which state that visual break is required and you cannot rely on an indicator alone for proving isolation.

Dear God your questions and lack of basic knowledge regarding high voltage transmission and distribution concern me, especially since you previous questions indicate you actually work in the field!

In your apparent position of responsibility you should not be asking these sort of questions of an online forum to cover up your apparent lack of knowledge in a field you are being paid to work in with very little margin for error. It is very unethical.

How's that 25MW 132kV grid-connected coal power station you were asking for help with last year going.

Haha.That 25MW plant is under evaluation

Yes, on CR4 it appears, based on your latest posted questions.

We are here to discuss matters of Engineering and such, not act as your free consultancy service or help you do your job, which I get a sense that you are doing.

I feel in my opinion you have crossed an ethical line and are taking advantage and abusing the point of this forum to make up for your Engineering short comings in a job position you are getting paid for.

Because the safety codes demand it...

There is more than one good reason to have line isolators on the busbar sections.

1. It disconnects the live line from the switchyard equipment on that circuit.

2. It provides a visual 'open isolation point' to anyone working on a circuit(s)

3. It allows for a earthing point to ensure the non line side equipment is safe to work on from backfeeds or feeds.

4. It allows for secure lockouts of that circuit, that it cannot be energised by an unothorisied person(s).

5. Anyone with experience in this field will know that CB's do not always operate and may not be in a safely maintained condition to operate properly, and be fully disconnected when tripped. So an isolator is a back and you will know if the CB did not trip fully, as you will draw and arc on the isolator when one opens it.

It is also a handy back up safety switch.